Motor stall overcoming device in a power typewriter

ABSTRACT

In an electric typewriter wherein the motor is liable to become stalled if two or more mechanisms become inadvertently connected for concomitant power operation, a device is manually operable for effecting temporarily a mechanical disruption in the motor drive to allow the armature of the motor to regain full speed running momentum and torque and when said device is restored after a time interval, the said momentum and torque becomes effective on the connected mechanism for completing their started operations.

United States Patent falegee? PATENTEDNnv 2 |97:

SHEET l UF 2 INVENTOR ATTORNEY BACKGROUND OF THE INVENTION In most marketed power-operated typewriters there are various conditions arising whereby resultant to inadvertent concomitant operations of two or more keys in the machine, different mechanisms are subject to power operations concomitantly or in overlapping-time relation so that when that happens the motor is apt tobecome stalled dueto encountered overload. The mechanisms which may be involved are:

The carriage return mechanism, the carriage backspacing mechanism, the case shift mechanism, the spacing mechanism and any one or more type actions in combination with others of the listed mechanisms or apart therefrom.

In many electric typewriters a key-locking device becomes effective to lock all keys when the electric switch on `the `machine is moved to an open-circuit position, so that ordinarily then none of the mechanism trains can be key tripped into condition for power operation before the switch is again closed. Therefore upon subsequent switch closure ordinarily none of the mechanism trains will stand key tripped for power operation. Nevertheless, if there is a power interruption to the machine due to failure of the power supply or simply due to a disconnection of the electric plug, it is obvious that then a multiplicity of mechanism trains by key operations could become conditioned for power operation. Obviously, `then upon power restoration the machine may become stalled as several conditioned mechanism trains are trying to become active.

Conventionally, most power-operated typewriters embody a motor of substantial starting torque and the procedure following a stall of the motor is to one or more times open and close the motor switch. The repeated starting torque so applied to the motor usually is sufficient to carry the instituted multiplicity of mechanism operations to conclusion. However, a motor with a weak starting torque is inadequate to conclude operations under the stated switch-operating procedure, because the armature would have to work instantly against the mass and load of the stalled mechanism and power-transmitting means.

According to the invention provision is made so that a shaded-pole motor, of low power, can be used which will serve the machine adequately for any single, normal power operation that needs to be executed. Obviously, such motor is liable to stall if a multiplicity of mechanisms are inadvertently key selected for power operation. However, according to the invention, each time the motor becomes stalled under the condition stated, a device may be manually operated, transitorily, in order to effect each time a temporary mechanical disruption in the normally motor-operated mechanical power-transmitting means and cause the armature to attain full running speed. The power supply to the motor is not shut off andthe stated mechanical disruption willallow the motor armature to rotate freely to regain quickly full speed torque and most importantly to store a considerable measure of kinetic energy. Therefore, if then the operated device is allowed to restore to its normal position, the full inertia of the then moving armature becomes effective on the power transmission to operate the selected mechanisms for completing their operations. lt may be necessary to employ the device more than once to effect the full completions of started operations.

IN `THE DRAWING FIG. l is a right-hand rear perspective view of a motor and a power transmission for power operating an electric typewriter and including a device which is operable to effect a transitory disruption in the transmission;

FIG, 2 is a plan view of the apparatus seen in FIG. 1, with the device operated to disrupt the transmission; and

FIG. 3 is a plan view similar to FIG. 1, but showing the device in normal position so that the transmission stands entrained with the motor.

DETAILED DESCRIPTION The typewriter of the invention embodies a lightweight,

low-powered, small dimension shaded-pole electric motor l0 which through a mechanical power transmission means in the form of a speed reduction drive, generally designated by the numeral 11, constantly drives normally a conventional power roll l2 on a shaft 13 in the typewriter at a greatly reduced speed.

Various conventional mechanisms, not shown, through `selective operations of control keys, are ,adapted to be selected for power operations by the rotation of the shaft 13 or power roll 12, to produce thereby power-typing operations, power case shifts, power carriage returns, power backspacing and power word-spacing operations.

The speed reduction drive 11 comprises on a motor shaft 14, a small diameter, grooved, composite structure V-belt pulley 15, later herein described in detail. Furthermore, said speed reduction drive 11 comprises a V-grooved large pulley 16, a V-belt 17 associated with said pulleys 15 and 16, a small `cog wheel 18 unitary with the large pulley 16, a relatively large cog wheel 19 unitary with the power roll 12 and a cog belt 21 connecting the cog wheel 19 for operation by the cog wheel `18.

Normally the motor 10 drives the power roll 12 and shaft I3 mechanismsas are key selected for power operation, become responsively power operated by the power roll 12 or its associatedshaft 13.

When inadvertently two of the typewriter mechanisms become connected to the power roll l2 or the shaft 13 for operation thereby, then the motor lill may be too weak to carry out thefmultiplicity `of operations, so that the speed reduction drive 11 and the motor l0 will become stalled.

The novel device of the invention is manually operable to effect a temporary disruption in the drive ll from the motor 10 to ,the power roll 12, therebyto allow temporarily the motor shaft14 to turn without restraint by the transmission 11 to regain full running speed whereby an armature l0' of the motor l0 will `store kinetic energy. Most efficiently the stated disruption is effected in a portion of thespeed reduction drive l1 close tothe,;motor 10. To this end, a composite pulley l5 on the motor shaft 14 comprises two axiallyspaced flanges 23, 24. These flanges 23, `24 are tapered where they axially face toward each other so as to afford normally a V-drive association with the V-belt 17. The flange 23 is integral with ahub 26 which has a screw 27 therein to fasten i't to the motor shaft l14. The other flange-24 has a long hub 28 whereby it is axially shiftably accommodated on the motor shaft 14. The pulley flange 23 has diametrically opposite lugs or keys 30 which f'tt slidably an aperture 3l reaching through the flange `24and slightly into -the hub 28. Normally the flange 24 faces the flange 23 in the close axial relationship seen in FIGS. 1 and 3, wherein theKV-belt 17 is engaged in a tight motion receiving fit, crowded radially outwardly on saidl flanges 23, 24. When the flange 24 has the stated position, the keys 30 abut the base of the aperture 31 in the hub 28.

The long hub 28 of the flange 24 has a peripheral groove wherein a C-ring 32 issprung to aord a collar. Beyond the C- ring 32, axially spaced from it, the motor shaft 14 has a collar 33 fast thereon and between it and the IC-ring 32 there is situated a strong compression spring 34 which tends always to movepulley flange 24 by its hub 28 into the close V-belt driving relationship with the flange 23 which is shown in FIGS. l and 3.

ln order to spread the pulley flanges 23, 24 to thereby render the composite pulley 15 incapable of driving the V-belt 17, there is provided a lever 35 which by a control button `36 is operable from the normal position seen in FIGS. l and 3 to the position seen in'FIG. 2. From` FIGS. 1 and 3 it will be seen that a forked portion`39 ofthe lever 3S is normally clear of a friction-reducing washer 52 which on said hub 28 is facing toward it from the C-ring32. The lever 35 is rockably supported flatwise on the outside of the inner righthand wall 37 of the typewriter, said wall 37 having a projecting lug 40 by which the lever 35 through a hole 4I therein is located, and the lever 35 having curve-ended ears 42 by which it rockably bears against the wall 37. The forked portion 39 straddles the hub 28. A light compression spring 44 on a stud 45 of the lever 35 which extends inside through the machine wall 37, serves to keep the lever 35 always seated by its ears 42 against the wall 37 and further tends to keep it in its normal position seen in FIGS. 3 and l. Therefore, as seen clearly in FIG. 3, the flange 24 of the composite pulley 15 through the spring 34 stands normally strongly pressed into V-belt driving relation with the pulley flange 23 and the speed reduction drive 1l is fully operative so long as no conflicting power operations are instituted by the operator and the machine does not become stalled.

The control button 36 for the lever 35 protrudes through a guide hole in a front panel 46 of the typewriter and has normally the position shown in FIG. 1. The button 36 is carried fast on a wire link 47 which has a pivotal joint with a cam lever 48 of bail form, the latter being fulcrumed on a stud 49 which rises from an ear 50 of the wall 37. The front end of the lever 35, under the urge of the light compression spring 44 bears nonnally on a low portion of a cam face 5l on the lever 48 all as seen in FIGS. l and 3. The cam lever 48 has a torsion spring 53 associated with it which constantly tends to restore it to the normal position seen in FIG. l.

lf the button 36 is operated to the limit of a stop 46 as in FIG. 2, the cam face 5l on the cam lever 48 will rock the lever 35 so that its forked portion 39, by contact with the washer 52, will slide the pulley flange 24 axially from the pulley flange 23 to the position seen in FIG. 2. Consequently, the V-belt 17 moves inwardly between the flanges 23, 24 and relaxes so that the latter are then incapable of driving it. The axial movement of the flange 24 is effected against the force of the compression spring 34.

Whenever a stalled condition of the motor and the drive ll arises, due to a different mechanism trains being selected for power operation conflictingly or in an overlapping time relationship, the shaded-pole motor l0 may become stalled. ln most such instances it would be of no avail to open and again close a conventionally provided motor switch. Obviously, at reclosure of such a switch, the armature l0' would immediately have to overcome the full load of the stalled condition of the reduction drive ll so that such condition of the motor l0 would almost certainly continue to persist.

According to the invention at hand, when the electric motor I0 and related transmission 1l becomes stalled, the operator is required to operate the button or control 36. This will disrupt the power drive train by effecting the separation of the pulley flanges 23, 25 so that the composite pulley 15 and thus the amature l0' is then free to turn and the torque of the motor I0 will quickly set the armature l0', the motor shaft 14 and the composite pulley in motion to come up to maximum running speed, whereby kinetic energy becomes stored in these parts.

When the button 36 is released, the cam lever 35 under the tension of the spring 44, consequently moves to the normal position seen in FIGS. l and 3, and the compression spring 34 consequently is enabled to force the pulley flange 24 into beltdriving relation with the pulley flange 23, and the belt 17 climbs between the bevels of the flanges 23, 24 into proper position. The kinetic energy which has been stored in the running armature l0', the motor shaft I4 and the composite pulley l5, along with the torque of the motor 10, consequently becomes effective on the stalled reduction drive 11 to set it in motion. In most instances, in view of the considerate stored kinetic energy, the motive force is sufficient to cause the stalled operations to be carried to full conclusion. However, it

tions. v

lf a stalled condition should arise due to several type bars having become power operated conflictingly, and moreover the type bars stand entangled in front of the platen, then it may be necessary for the operator to untangle such type bars by hand to free them for return to rest position. In some instances such untangling is best done if the motor torque is temporarily removed through the temporary operation of the button 36.

It is to be observed that the disruptable motiontransmitting connection which the flanges 23, 24 afford in conjunction with the belt 17 actually is a form of a mechanical clutch in a mechanical transmission drive.

What is claimed is:

l. In an electric typewriter having typing and other mechanisms which under key control are individually selectively connectable for operation by a nonnally continuously driven operating means to execute their assigned functions and thereupon become automatically disconnected,

a shaded-pole motor comprising a motor shaft extending transversely of the typewriter,

an armature on such shaft,

a V-belt speed reduction drive normally operative to drive said operating means continuously by said motor shaft comprising,

a composite V-belt pulley on said motor shaft having a first flange member on and unitarily rotatable with said motor shaft and a second flange member which with reference to said first flange member is shiftable axially of said motor shaft from a normal V-belt driving relationship with said first flange member to a drive-interrupting relationship therewith,

said second flange member having an extending hub by which it is carried shiftably axially on said motor shaft,

an annular element on said hub near the extending end thereof affording a shoulder facing toward but being spaced from said second flange member,

a collar fast on said motor shaft and axially spaced from the extending end of said hub,

a compression spring situated on the motor shaft and interposed between said collar and said hub to urge said second flange member into belt-driving relation with said first flange member,

a lever having a pivot axis in a vertical plane at a location forward of the motor shaft and having a rearwardly reaching forked portion for engaging said annular element to shift said second flange member on said motor shaft into a drive-interrupting relationship with said first flange member,

spring means pivotally biasing said lever for its forked portion thereof to stand normally axially of the motor shaft clear of the annular element, and means to control said lever comprising a control element at the front of the machine and means operable by said control element to operate said lever, to engage said annular element and shift the second flange member positively to said drive-interrupting relationship with said first flange member.

2. The invention defined in claim l, said control means including a pushbutton, and a cam element operable by said pushbutton to positively operate said lever to effect the shift of said second flange member on the motor shaft positively into said drive-interrupting relationship with said first flange member. 

1. In an electric typewriter having typing and other mechanisms which under key control are individually selectively connectable for operation by a normally continuously driven operating means to execute their assigned functions and thereupon become automatically disconnected, a shaded-pole motor comprising a motor shaft extending transversely of the typewriter, an armature on such shaft, a V-belt speed reduction drive normally operative to drive said operating means continuously by said motor shaft comprising, a composite V-belt pulley on said motor shaft having a first flange member on and unitarily rotatable with said motor shaft and a second flange member which with reference to said first flange member is shiftable axially of said motor shaft from a normal V-belt driving relationship with said first flange member to a drive-interrupting relationship therewith, said second flange member having an extending hub by which it is carried shiftably axially on said motor shaft, an annular element on said hub near the extending end thereof affording a shoulder facing toward but being spaced from said second flange member, a collar fast on said motor shaft and axially spaced from the extending end of said hub, a compression spring situated on the motor shaft and interposed between said collar and said hub to urge said second flange member into belt-driving relation with said first flange member, a lever having a pivot axis in a vertical plane at a location forward of the motor shaft and having a rearwardly reaching forked portion for engaging said annular element to shift said second flange member on said motor shaft into a driveinterrupting relationship with said first flange memBer, spring means pivotally biasing said lever for its forked portion thereof to stand normally axially of the motor shaft clear of the annular element, and means to control said lever comprising a control element at the front of the machine and means operable by said control element to operate said lever, to engage said annular element and shift the second flange member positively to said drive-interrupting relationship with said first flange member.
 2. The invention defined in claim 1, said control means including a pushbutton, and a cam element operable by said pushbutton to positively operate said lever to effect the shift of said second flange member on the motor shaft positively into said drive-interrupting relationship with said first flange member. 